<template>
  <ul class="list">
    <li class="item"
      @touchstart.prevent="handleTouchStart"
      @touchmove="handleTouchMove"
      @touchend="handleTouchEnd"
      @click="handleLetterClick"
      v-for="item in letters"
      :ref="item"
      :key="item ">
    {{item }}
    </li>
  </ul>
</template>

<script>
export default {
  name: 'cityAlphabet',
  data () {
    return {
      touchStatus: false
    }
  },
  props: {
    cities: Object
  },
  computed: {
    letters () {
      const letters = []
      for (let i in this.cities) {
        letters.push(i)
      }
      return letters
    }
  },
  methods: {
    handleLetterClick (e) {
      this.$emit('change', e.target.innerText)
    },
    handleTouchStart () {
      this.touchStatus = true
    },
    handleTouchMove (e) {
      if (this.touchStatus) {
        const startY = this.$refs['A'][0].offsetTop
        const touchY = e.touches[0].clientY - 79
        const index = Math.floor((touchY - startY) / 20)
        if (index >= 0 && index <= this.letters.length) {
          this.$emit('change', this.letters[index])
        }
      }
    },
    handleTouchEnd () {
      this.touchStatus = false
    }
  }
}
</script>

<style lang="stylus" scoped>
@import '~styles/varibles.styl'
.list
  display flex
  flex-direction column
  justify-content center
  position absolute
  top 1.58rem
  right 0
  bottom 0
  width 0.4rem
  color $bgcColor
  .item
    line-height 0.4rem
    text-align center
</style>
